Will Dunham
WASHINGTON (Reuters) – Scientists are observing the behavior of a supermassive black hole that exhibits an unusually chaotic eating habit.
They used radio telescopes primarily in New Mexico and South Africa to observe the black hole, which lies at the center of a galaxy far away from our own Milky Way, continuing to eject fast-moving jets of material after tearing apart and devouring a star that mistakenly wandered too close.
What was unusual about this fatal encounter between stars was the intensity and duration of the black hole’s post-meal indigestion.
The material left behind by the star does not start to be ejected into space until it is torn into gaseous components by the black hole’s gravity for two years. But the jet has now been in space for six years—longer than previously observed—and continues to intensify, becoming one of the most powerful single events ever detected in the universe.
“This exponential increase in the brightness of this source is unprecedented,” said University of Oregon astrophysicist Yvette Cendes, lead author of the study published Thursday in The Astrophysical Journal. “It’s now about 50 times brighter than when it was first discovered, which is incredibly bright for an object in radio waves. This has been going on for many years and it shows no sign of stopping. It’s very unusual.”
Black holes are extremely dense objects whose gravity is so strong that not even light can escape. This black hole is about 665 million light-years away from Earth. A light year is the distance that light travels in one year, or 5.9 trillion miles (9.5 trillion kilometers).
The black hole’s mass is about 5 million times that of the sun. This makes it roughly comparable to the supermassive black hole at the center of our galaxy, which is about 4 million times the mass of the Sun.
The doomed star was a type of star called a red dwarf, with a mass about one-tenth that of the Sun.
The event horizon is the point of no return for matter attracted by the black hole’s gravity. When a star is pulled apart by a black hole, it’s called a tidal disruption event because it’s caused by the same gravitational dynamics as ocean tides on Earth.
“Any object that gets too close to the black hole’s event horizon has the potential to be torn apart by tidal forces and stretched into a long string of fragments, a process known as ‘spaghettification,'” said Kate Alexander, an astrophysicist at the University of Arizona and study co-author.
“After the star is torn apart, some of the gas falls toward the black hole and is heated, and the black hole begins to eat the star. The bright radio light we see with telescopes is produced by stellar material that approaches but never actually crosses the event horizon—like a fussy baby chewing food and then violently spitting it out instead of swallowing it,” Alexander said.
Researchers aren’t sure why this tidal disruption event and its jets, formally known as relativistic jets, are so spectacular.
“As for what causes relativistic jets, we don’t actually know, and that’s an active area of research. It could be related to the magnetic field around the black hole, but it obviously has to be something unusual as well, otherwise we’d be seeing more of these,” Seiders said.
The question now is how long the jet will continue to intensify. Researchers suspect it could peak later this year or next year.
“After the emissions peak, it should slowly recede, so we may still be able to see it for a decade or more,” Alexander said.
(Reporting by Will Dunham; Editing by Rosalba O’Brien)
